Mobile door closure interrupting detector

Abstract

The present invention relates to an alarm device for doors in vehicles which is located in a hollow rubber tube and gives alarm as the tube is compressed. The device can be adjusted to be sensitive by placing in one end of the tube a light transmitter and in the other end a light receiver producing a signal which changes according to the light intensity received by the receiver and by compensating slowly occurring changes in said light intensity so that the light intensity of the light transmitter in a corresponding manner is corrected.

What I claim is: 
     
       1. A signaling device for vehicles comprising: a tube having resilient walls;   a detecting element arranged within said tube for detecting the compression thereof, said detecting element including a light transmitter and a light receiver between which a light beam passes, said light receiver producing an output signal indicative of the intensity of said light beam transmitted through said tube by said light transmitter;   a first detection circuit means coupled to said light receiver for producing a signal in response to a change in said output signal above a predetermined limit occurring within a predetermined time, said change being caused by a compression of said tube;   a second detection circuit means coupled to said detecting element for producing a compensating change in the intensity of said light beam emitted by said light transmitter in response to a change in said output signal occurring beyond said predetermined time and an automatic gain control circuit which is coupled between said delay circuit and a current generator coupled to said light transmitter, said automatic gain control circuit producing a correction in the intensity of said light beam of said light transmitter.   
     
     
       2. A signaling device according to claim 1, wherein said delay circuit has a delay time of about 10 s. 
     
     
       3. A signaling device according to claim 1, wherein to said automatic gain control circuit is connected a comparator which compares said signal of said automatic gain control circuit fed to said current generator for said light transmitter with a given limit voltage and an alarm means connected to said comparator for producing a failure alarm when said limit voltage is exceeded. 
     
     
       4. A signaling device according to claim 1, wherein said light transmitter comprises a bulb or an LED and said light receiver comprises a light diode, a light transistor or a light resistor. 
     
     
       5. A signaling device according to claim 1, wherein said tube having an inner surface provided with a light reflecting coating.